In general, acrylonitrile is prepared on industrial scale by an ammoxidation reaction of an unsaturated hydrocarbon, i.e., propylene. However, it has been reported that propane instead of propylene, can also be employed in the ammoxidation reaction more economically; and, therefore, the development of catalysts for the ammoxidation of propane, has been one of the most important tasks in the art.
On the other hand, prior art catalysts which function to produce acrylonitrile, mono- or binary component oxide metal catalysts, have not been employed in industrial process in a practical manner, due to their low activity and selectivity. In this connection, studies on the ammoxidation reaction of propane to acrylonitrile have been extensively carried out in Japan and U.S.A. in order to develop highly active and selective multicomponent oxide catalysts which are practically applied for producing acrylonitrile compounds.
Under the circumstance, a number of multicomponent oxide catalysts have been suggested as highly active and selective catalysts, which are prepared by the addition of alkyl halide such as bromoethane (0.2 mole %) to Bismuth-iron (Bi--Fe) oxide catalyst, Uranium-Antimony (U--Sb) oxide catalyst and Bismuth-Tellurium-Molybdenum (Bi--Te--Mo) oxide catalyst, respectively [see: U.S. Pat. Nos. 3,670,008; 3,816,506; and, 3,833,638]. However, special materials to prevent corrosion should be employed in reactors or plants because the halogen compound such as bromoethane gives rise to strong corrosiveness.
On the other hand, U.S. Pat. No. 4,609,502 teaches a process for preparing acrylonitrile by the ammoxidation, which employs propylene produced by dehydrogenation of propane. However, said dehydrogenation process of propane has caused undesirable economical problems in light of plant investment in comparison with the ammoxidation of propylene.
G. Centi et al. reported that introduction of aluminum oxide (Al.sub.2 O.sub.3) to the Vanadium-Antimony (V--Sb) oxide catalyst, improved in terms of selectivity for acrylonitrile, grounded on the change of catalyst structure: however, said catalyst was not applied on industrial scale because of its limitation on selectivity and performance [see: G. Centi, R. K. Grasselli, E. Patane, F. Trifiro, in New Developments in Selective Oxidation, Elsevier Science Pub.: Amsterdam 1990, 515].
Under the circumstances, several catalysts have been proposed as effective catalysts under high level of propane in the reactants: for example, multicomponent catalyst which various metal components was added to Vanadium-Antimony (V--Sb), mixed oxide catalyst (U.S. Pat. No. 4,797,381), Bismuth-Cerium-Molybdenum (Bi--Ce--Mo) mixed oxide catalyst and Bismuth-lron-Molybdenum (Bi--Fe--Mo) mixed oxide catalyst (U.S. Pat. No. 4,760,159); and, multicomponent catalysts produced by mixing the latter two catalysts (U.S. Pat. No. 4,877,764).
Some other literature also discloses that the multicomponent oxide catalyst known as effective for selective oxidation reaction, provides a good performance relatively, and selective conversion of propane to acrylonitrile depends on the kinds of metal elements of multicomponent oxide catalyst and the amount of each component. However, it was still undesirable to use said catalysts on industrial scale owing to their low activity and selectivity. Therefore, need has continued to exist for the development of a highly active and selective catalyst, which is practically employed in industrial process.